Electrical measuring instrument.



, A. LE R. ELLIS. ELECTRICAL MEASURIIIG INSTRUMENT.

' APPLICATION rum) JULY 2a. 1907.

1,023,304. Patented Apr. 16, 1912.

Illllllllllllllilllllll gnnmummw EYM W I AT Y ' [VI/ENDH v manent change-in the field. of force.

. UNITED STATES PATENT OFFICE.

ALVARADO LE ROY ELLIS, OF LYNN, MASSACI IUSETTS, ASSIGNOR TO GENERAL ELEC- TRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRICAL mmsna'me msmnmnnr.

Specification .0! Letters Patent.

Patented Apr. 16,1912.

Application filed July 29, 1907. Serial No. 385,974.

Toall whom it may concern:

.Be it known that I, ALvAnAno l1. Ennis, a citizen of the United States, residing at Lynn, county of Essex, State of 'Mas's'achusetts, have invented certain new and use in] Improvements in Electrical Measurlng Instruments, of which the following. 15 a strength of the field of force produced bythe permanent magnet,-.and any manipulation of the instrument which affects or alters the magnetic circuit may produce a per- The moving coil is usually mounted to swing in an annular air-gap between a fixed core generally ot a circular cross-section, and polepieces having faces concentric with the core. in these instruments as heretofore construct ed, the moving coil is so mounted in relation to the core that the core as well as the coil unust be'removed from the instrument if any changes or adjustments-are to be made on the moving-system, and unless the core is replaced very exactly in its origmal position between the pole-places of the permanent magnet the magnetic circuit may permanently altered.

.The moving system should be made as light as possible and should also have some;

' device to exert a damping effect. In many instruments heretofore constructed, the coil is supported upon some sort of a core or frame, the damplng disk or similar arrange- .ment is secured to the frame, and the pointer for indicating the movement of the coilis secured to one of the pivots of the coil,

'eithor bv tightly engaging, the pivot or by being Yhreaded on the pivot and held in position by a lock-nut. These constructions are expensive and make the weight of the moving system considerably more than that.

ofthe coil.

. The object of my invention is to provide an electrical measuring instrument of the.

permanentmagnet type, in. which the movingsystem may be removed without altering or attending the magnetic circuit of the permanent magnet; to provide an improved means of attaching the pointer to the mov- ,ing coil which will decrease the 00st of concore, preferably circular in cross-section, be,-

tween the pole-pieces of the permanent magnet, thereby forming an air gap for the moving coil in which the field of force is very denseand uniform. The core .is permanently held in fixed relation to the polepi'eces of the magnet and the moving system is so supported that it may be removed from the air-gap between the coreand the pole'- pieces 0 the magnet without disturbing the relation of the core to the magnet, and without affecting in any way the magnetic circuit. The moving system is made exceed ingly light by using a universally wound self-supporting'moving coil, to which the pointer is directly attached in any suitable manner, preferably by a clamping means which also acts as a damping disk. By this construction all superfluous weight is eliminated, the cost of attaching the pointer to a pivot of the coil is avoided, and the pointer oes not exerta twisting Iitrain upon the pivots and: their attaehme s to the coil. The pointermay be directly attached to the damping device, and is preferably stamped out of aluminum with an integral part thereof forming a ring which engages the coil and forms part of theelamping means for attaching the pointer to the coil. The ring may have fingers bent at an angle .to the plane of the ring to extend through the coil and position theringand pointer with relation to the coil.

My invention will best be understood in. connection with the accompanying drawings which are an illustration of oneembodiment of my invention and in which'.

Figure 1 is a top plan view of an instrument embodying my invention; Fig. 2 a sectional .view of the instrument shown in Fig. 1; Fig; 3 a plan view of the aluminum stamping from which the pointer and the means for attaching it to the coil are formed; Fig. 4 a perspective view of the pointer and clamping'means for holding it to 'the moving coil, part or" the coil being removed; Fig 5 a similar view showing a construchold the magnet in proper position and are preferably made "ofbrass or other non-- tion for securing a strong damping effect;

Fig. 6 is a view in perspective of theselfsupporting moving coil without a pointer or pivots and Fig. 7 is a partial section of the instrument taken on line 7-7 of Fig. 1.

I have shown .my invent-ion applied' to a portable galvanometer, mounted" in a casing consisting of a base 1', sides 2, and .a topf3l containinga window 4 through which the scale of the instrument may be observed. The casing is "provided with bindingcposts 5 through which the current to be measured is led to-the instrument.

means *of a support 7 and clamps 8 forming part of? another support 9 firmly secured to the-base'l. The supports '7 and 9 rigidly magnetic'mater'ial. The pole-pieces ,of the magneto which maybe inodified as desired. prefe'rably'have semi-circular pole faces and a core 10 0f soft iron,preferablycircular in cross section, is'permanently 'and rigidly monntedf between the-"pole-piecesbf' the to set itself parallel to the axis of "the magnet 6 being firmly held in position on the support 9 by means e rnest-screw 11 and guiding'pins 12'rigidly secured to the sup-j port andexlendinginto guide openings in the corc 10.-- The relation of the core 10 to the pole pi'ecesof the magneto is fixed when the instrument is assembled and is 4 never afterward ch ahged. so that the "magnetic circuit remains the same as when'the lIlStI'llment wasassembled. v y v The moving system of the instrument comprises a 'coil 13 whichis self-supporting and very' compact on account of being uni versally wound according to the disclosure of U. SJ'Patcnt 486.745- granted November 22, 1892. to Simon Wardwell, Jr. The coil is wound-in accordance with the disclosure of said patent 'to bring the 'wires'in successive layers, and the wire inl'ea'ch turn of each layer extends'to the cndct the coiland is then reversed at a pointbeyond the point at which the wirc of thepreceding turn is reversed. thereby bringing the points at which the wircsiarerevcrscd in substantially the same plane-and laying thewire of each turn parallel tothat-of thepreccding turn. The moving coil wound in the manner above de scribed norma 1y loosely-encircles the core and swings in the annular air-gap between 'the cylindrical core and pole-piece :of the magnet, movingat an angle totheax'is of the coreaud ,tending when current flows core. The coil has pivots 14 consisting of a hardcncdstcel pointin'vthe: end of a short stem of aluminlnn. attached to the coil in anyjsuitahle manner, The pivots work 'in jewels carried ina bracket or support 7 '16 so mounted with relation to the magnetic system that the moving coil may be shifted longitudinally of the core and out of the annular air-gap without in any way afi'ect- 111g or altering the relation of the core 10 to the'magnet '6. The bracket 16 is preferably secured tothe core 10 by means ofa set-screw v 17 and guiding means comprising pins 18 engaging guide openings'in the core.- The moveme nt of the coil when current flows through it is resist-ed by spiral springs .19 r and 20, eachof whiclrhas one end attached to a" pivot 14. the twopivots being in electrical connection with the two ends of the coil, The other end of the lower spring 19 is attached to a binding-post 21. carried by and insulated from the bracket .16 and connected through a wire 22 .to one oft-he binding-posts 5, ,so .that current can flow from one binding-post 5, through the wire 22, the binding post 21', and the spring 19, to the coil 13. 'The other end of the upper, spiral spring 20 is in metallic connection with the bracket 16 through an adjusting arm '23 which swings about the sup ort for the upper jewel 15 as a center and is shifted for the purposev of varyingthe normal. position of the movingsysteinby means of an adjusting knob 24 extending. through the top 3 of the casing. for the instrument. The brackctlfi'is inclectrical connection with the other binding post through the core 10.

the'support 9 and a wire leadingjtosaid binding post, completingthe-circuit through 'the'eoil. Y I

In'ordc'r to improve the construction of the moving systcm andrcnder it aslight as possible the pointer for indicating the displacement of'the moving coil is attached directly to the coil 13. This construction avoids the expenseland other obiections of directly attaching the pointer in various ways to one of the pivots which carries the moving-coil. The pointer 25 may be attalched to the coil inany suitable manner, 1

preferably by a clamping device which also acts as a damping disk. In the preferred construction an v aluminum stamping or punching'is made m the i-form shown in Fig.

3. comprising the pointer 25 witha ring 26 integral therewith, and fingers 27 extending radially inward froni'the inner edge of the ring. The pointer and fingers'are then bent so that the-pointer extends in one direction from the ring 26. while the fingers extend in *the-other direction at right angles from the plane of thering, as shown in Fig. 4. The

fingers 27 form 'partofthe'surfac'e of a cylinder of substantially the same diameter as the inner diameter o-f the coil 13. conforming to-the shape thereof. The coil is slipped over these fingers until one side thereof comes into engagement with the ring 26, Another ring 28,;preferably considerably thicker than the ring 26, is the'n'slipped over the ends of the fingers 27 until it comes into engagement with the other side of the coil 13, after which the ends of the fingers '27 are bent outwardly, as shown in Fig. 4, whereby the various elements of the moving system are. firmly clamped to the moving coil 13. The aluminum structure comprising the fingers 27 and the clamping rings 26 19 weight of the ring 28 partially counterbalances the weight of the pointer 25.

If the instrument has high torque it may i be desirable to exert a greater damping effeet than can be secured with the above described construction, and an increased damping may be obtained by the construction shown in Fig. 5, in which the pointer is held in engagement with the coilby a structure consisting of metallic; tubing 27' 'having a flange 27 at one end in engagement with the ring 26 and a flange 28 at the other end in engagement'with the coil. The tubing and flanges damp the movement of the coil very means for securing this pointer to the coil.

A scale 29 for measuring the extent of movement of thepointer 25 is secured to the magnet 6 by mea 'nsof clamps 30, while extreme movements of the pointer are prevented by stops 31, preferably consisting of spring wire secured tn the support 9 and carrying a cushion of rubb r or similar material in a ")osition to he engaged by the pointer 25, at the extreme points of its movement. v I

My invention may begembodied in many other forms than that shown and described, and I therefore do ndt wish to be restricted to the precise, form shown but intend to cover by the appended claims all changes and modifications 'within the spirit and scope of my invention.

WVhat I claim as new and desire to secure by LettersPatent of the United States, is,-

1. In a measuring instrument, the combination with a magnetic system-comprising concave pole pieces, a cylindrical core mounted concentric therewith to form an annular air-gap, and a fixed support connected to one end of said core to hold it in position,-

of a circular coil arranged in a plane at an angle to that axis of the core passing through said support, said cpil being'pivoted to encircle said core and swing in said airg p 2. In a measuring instrument, thecombination with a magnetic system comprising a magnet with confronting pole surfaces of which the elements are parallel to a straight line and a core mounted between said pole pieces with its axis substantially parallel to said line, of apivoted coil mounted to encircle said core and toswing about an axis intersecting the axis of said core, and a supmagnetwith confronting p I and 28 acts as a damping disk, and the quickly and effectively and form clamping porting bracket'for said coil movable parali lelto the elements of said pole surfaces and at right angles'to the second named axis to withdraw said coil from between the polepieces. I v

3. In a measuring instrument, the combi-' nation with a magnetic system'comprising a surfaces of which the elements are parallel to a straight line and a core mounted between said pole pieces, of'a. pivoted coil mounted'to encircle said core and to swmgabout an axis intersecting said core, and a supporting bracket for said coil detach-ably secured to the core and movable at right anglesto said axis to withdraw said coil from'betwee'n said pole pieces.

4. In a measuring instrument, the 'combi nation with a magnetic systemromprising a magnet with confronting pole surfaces of -85 which the elements are-parallel to a straight v line and a core mounted between said ole pieces, of a pivoted coil mounted toenclrcle said core and to swing about an axis intersjecting said core, and means for causing sa'id bracket to move parallel to the-elements of said pole surfaces and at right angles to said said coil detachably secured tosaid Y core,

and coiSperat-ing guides on said core and said bracketto maintain said bracket in definite relation to said pole surfaces-during movement of the bracket.

6. In a measuring instrument, the combi .nation with the moving coil, of a ring for' engaging one side of the coil and having fingers'passing through the'coil, and a sec,- ond ring for encircling said fingers and en-' gaging the other side of the c'pil.

7. In a measuring instrument, the combination with the moving coil, of a ring havin g fingers integral therewith and extending at an angle toithe plane of the ring, and a second ring for encircling the fingers and. holding the coil in engagement with the first ring, the ends oi the'fingers being bent. I

outward to hold the second ring in position.

8. In a measuring instrument, the combination with the imovi ig coil, of a ring'having a-pointer ex ending from one side thereof and fingers f r engaging the cdil extend- 12E ing from the 0 her side, and a second ring for engaging aid fingers near the end thereof. I 1 9. In a meas'uting instrument, the combl nation with theitno'ving; coil, of a ring for 1315 one sideofthe coil carrying a i i pointer and having integral fingers for pa ss ingthroughthe coil, and a second ring for encircling the. fing on th sideof uthe coil. w

. 10.111- a measuring instrument, the combination with [the moving coil, of a pointer,

and-damping meanscooperating with said pointer to hold it in frictional engagementwiththe coil.

11,.In a.measuring'instrument, the combination witha moving-coil, of a pointer for 'rmdicatingfthe movement of said coil, and damping means in; operative relatlon wlth' saidpointer and said :co'il forming a clamp to engage said-coil and thereby hold said' pointerinposition.

12. In 'a-.measuring instrument, the' -com ybination with a self-supporting moving coil, ;of a; pointer,

and a metallic structure extending through the coil and conforming e thereof: for clamping the ictional engagement with the bmation with the moving coil, of'a pointer '1 :sald-zcoil to- ,eo U; i

- '14-.' Ina-measuring instrument, the com I binationwith a magnetic system comprisof which the elements are straight line;

sta'ntiallyparallel to-said-straight line im-x,

having a ringintegral therewith, and {clampin means in engagement wlth said ring and old said ring in position'on the ing amagne't with confronting pole surfaces w v 1.; a core having its ax s submovably molinted between said'fpol'c surfaeesiand spaced apart therefrom, moving'co'il-pivotally moun'tedto encirfcle s aid -r I and the core about, an

parallelto a core and swing between the' pole surfaces axis intersecting the axis of said core, and a support for the coil movable relatively to the core and parallel to saidpole surfaces. 15. In a measuring instrument, the combination with a magnetic system comprising a magnet with'coneave polepieces and a cylindrical core immovably mounted concentric with said pole pieces, of a'moving coil pivotally mou'nted to encircle said core, and a coil support movable longitudinally of the core whereby the coil may be removed without affecting the magnetic circuit of the system.- 4 r 16. In a measuringinstrument, the combination with a magneticjsystem having concave poles and a cylindrical core permanently positioned between said poles to form an annular air-gap, of a mov ng coil pivoted to swing about anaxi's intersecting the removably mounted thecoil in said gap.- y 17. In a measuring" instrument, the combination with a magnetic system comprising a fixed cylindrical core, of a moving -coil pivoted to encircle sai'dcore' to swing about an axis intersecting s'aid core, and a coil support detachably secured to and movable in position to maintain longitudinally of thecore whereby the'movmg coil may be removed the magnetic circuit.

my hand this t-w VARADO LE ROY- ELIA j Witnesses-z Cements -A. BAnna nm- J0 gwithout altering In witness whereof, Ihave hereunto'lsdt W enty-fifth day of J uly,j,

00 axis of said core, and a support for said COIl 

